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4x4 Matrix Keyboard Small:A keypad is the most widely used input devices of a microcontroller. In order to use it effectively, we need a basic understanding of them.

Many application requires large number of keys connected to a computing system. Example includes a PC keyboard, Cell Phone keypad and Calculators. If we connect a single key to MCU, we just connect it directly to I/O line. But we cannot connect, say 10 or 100 keys directly MCUs i/o. Because :

It will eat up precious I/O line.

MCU to Keypad interface will contain lots of wires.

We want to avoid all these troubles so we use some clever technique. The technique is called multiplexed matrix keypad. In this technique keys are connected in a matrix (row/column) style.